In today's vehicles, the human-machine interaction (HMI) is becoming increasingly complex. The number of in-vehicle comfort functions is increasing as are the number of maneuverable buttons in the vehicle. Haptic interfaces for in-vehicle functions are now commercially available. Thus, haptic interfaces are a realistic approach to an aesthetically and ergonomically improved HMI. That is, without increasing the visual load on the driver. However, as often is the case with new technologies, some haptic interfaces might have been put into operation before being studied and evaluated sufficiently, e.g. being potentially "safety critical". The objective of this paper is to contribute in bridging the gulf between application and research concerning implementation of haptic interfaces for in-vehicle comfort functions. Two studies are reported in the paper. Firstly, a simulator study where a haptic/graphic interface is evaluated against a traditional interface with maneuverable buttons for in-vehicle comfort functions. Secondly, an experimental study that still is in the planning phase. The study aims at investigating the interaction effects between haptic and visual feedback in a haptic/graphic interface.